I. Field of the Invention
This invention relates generally to the mixing of materials and to the analysis of the results of such mixing. In particular, the invention relates to improved methods, apparatus and systems for mixing materials and the analysis of the results of such improved mixing. The present invention is particularly useful in automated chemistry analyzers for determining the presence and levels of one or more selected constituents in relatively small biological liquid samples.
II. Description of the Prior Art
Numerous automated clinical analyzers are known and widely used in hospital clinical laboratories. An example of such an analyzer is the multi-channel type analyzer.
A multi-channel analyzer is one in which a series of different tests are performed simultaneously by the analyzer, and in parallel with one another. Such an analyzer can be best visualized as a series of batch analyzers operating in parallel wherein each channel performs a single analysis test. The multi-channel type analyzer generally utilizes a liquid reagent to react with the particular constituent being tested in the sample and a photo-optical system to read the optical absorbence of the sample which corresponds to the level of the constituent in the sample.
Although this type of automated analyzer has received wide acceptance in the clinical laboratory certain drawbacks are associated with its use. For example, although the multi-channel type analyzer is reliable due to its simplicity, cost effective for large number of samples and has a relatively high test throughput rate, it is limited in the sense that it can only be effectively utilized to perform a single constituent analysis at a time on a relatively large number of samples. In addition, such analyzers are not capable of performing emergency "stat" tests due to their relatively long and complex set up time and their inherent inability to economically analyze a single test sample.
A further significant disadvantage found is that although they can simultaneously perform tests for multiple constituents on the same sample, generally all of these tests must be performed for every sample whether desired or not. This results in a waste of both sample material and the reagents used in the unnecessary tests. Furthermore, due to the fact that multiple discrete and dedicated channels are utilized in such an instrument, there is significant duplication of numerous components which adds to the complexity and expense of the overall instrument.
An automated single track clinical analyzer which avoids the above-described drawbacks is described in commonly owned U.S. Pat. No. 4,528,159, issued July 9, 1985, entitled, "Automated Analysis Instrument System". By using a unique photo-optical system, described in commonly owned U.S. Pat. No. 4,477,190, issued Oct. 16, 1984, entitled, "Multichannel Spectrophotometer", greater flexibility of analysis at each analysis station is achieved. This is because the photo-optical system employs fiber optic bundles or similar light guides to transmit variable wavelengths of light to each analysis station from a single light source.
The single track analyzer utilizes a disposable cuvette belt formed form thin plastic film and defining a series of discrete reaction compartments (cuvettes) which are transported in line ahead through the instrument. Such a cuvette belt is described in commonly owned U.S. Patent Application Ser. No. 284,842, filed July 20, 1981 entitled, "Cuvette System For Automated Chemical Analyzers", now abandoned. This belt provides handling flexibility and avoids the cross-contamination associated with flow-through cuvettes as well as avoiding the washing required for reusable cuvettes.
The earlier clinical analyzers discussed above employed liquid reagent, and mixing of the reagent with the diluent prior to addition of the biological sample. One method of achieving such mixing was by shooting a stream of the liquid reagent into the cuvette so as to produce a vortex-type mixing process. A preferred feature of the analyzer disclosed in U.S. Pat. No. 4,528,159 is that it is adapted to utilize dry particulate reagents, preferably in tablet form, which are dispensed into the cuvettes from a rotating carousel which can hold a large number of doses. A preferred embodiment of tablet dispenser is described in commonly owned U.S. Pat. No. 4,405,060, issued Sept. 20, 1983, entitled, "Tablet Dispensing Device". In order to effect dissolution of the dry particulate reagent within the diluent prior to addition of the biological sample, the reagent and diluent are mixed by ultrasonic means.
An improvement in the reliability and controllability of the analysis of liquid samples, particularly liquid biological samples, is achieved by mixing the contents of the cuvette after addition of the sample by directing an air jet at an acute angle against the surface of the liquid in the cuvette. Particularly good mixing is obtained when the air jet is directed at the liquid surface adjacent its junction with the wall of the cuvette. The optimum point of contact of the air jet with the liquid surface is the meniscus formed at the junction between the liquid surface and the wall of the cuvette.
The combination of directing the air jet against the liquid surface adjacent its junction with the wall of the cuvette and directing it at an acute angle to the surface producing a horizontal component has the beneficial effect of creating a vortex which produces a thorough mixing of the contents of the cuvette. Thus, a whirling or circular motion is induced in the contents tending to form a cavity of vacuum in the center and to draw the materials at the edge towards the center thus providing an effective mixing action. Particularly where the air jet hits the contents of the cuvette in the meniscus region, the contents tend to be raised up the wall of the cuvette opposite where the air jet hits the contents creating a particularly effective vortex producing very good mixing of the sample with the diluent and reagent. Thus, a particulate reagent will become totally suspended within the diluent and the sample optimizing the reaction of the sample therewith. This improved mixing technique is described in commonly owned U.S. Patent Application Ser. No. 848,851, filed Apr. 4, 1986, a continuation of Ser. No. 575,924, filed Feb. 1, 1984, now abandoned entitled, "Clinical Analysis Systems and Methods", the disclosure of which is hereby incorporated by reference in its entirety herein.